Indometacin as prophylaxis for heterotopic ossification after the operative treatment of fractures of the acetabulum.

Our study was designed to compare the effect of indometacin with that of a placebo in reducing the incidence of heterotopic ossification in a prospective, randomised trial. A total of 121 patients with displaced fractures of the acetabulum treated by operation through a Kocher-Langenbeck approach was randomised to receive either indometacin (75 mg) sustained release, or a placebo once daily for six weeks. The extent of heterotopic ossification was evaluated on plain radiographs three months after operation. Significant ossification of Brooker grade III to IV occurred in nine of 59 patients (15.2%) in the indometacin group and 12 of 62 (19.4%) receiving the placebo. We were unable to demonstrate a statistically significant reduction in the incidence of severe heterotopic ossification with the use of indometacin when compared with a placebo (p = 0.722). Based on these results we cannot recommend the routine use of indometacin for prophylaxis against heterotopic ossification after isolated fractures of the acetabulum.

Increased distraction rates influence precursor tissue composition without affecting bone regeneration.

The effect of increased distraction rate on bony tissue differentiation was studied using a paired bilateral model of rat femur lengthening. After a 6-day latency period, one randomly selected femur for each rat was distracted at 0.5 mm/day (normal rate) for 12 days, and the contralateral femur was distracted at 1.5 mm/day (increased rate) for 4 days. Femoral lengthening for each side was 6.0 mm, leaving the increased rate leg with an extra 8 days of consolidation compared with the normal rate limb. Group I rats (n = 9) were killed at day 18 postsurgery and analyzed for cartilage tissue composition and distribution. Group II rats (n = 7) were killed on day 36 postsurgery and analyzed by three-dimensional microcomputed tomography (MCT) for changes in new bone volume. Digital color analysis of slides stained with type II collagen antibody showed increases in cartilaginous tissue formation on the increased rate side (1.51 mm2 vs. 0.83 mm2; p = 0.10). No differences in new bone volume were detected between increased rate limbs and their contralateral controls (46.13 mm3 vs. 42.69 mm3; p = 0.63). These findings suggest that intermediate distraction rates may influence precursor tissue composition without affecting the final amount of new bone formed. Because damage to the tissue was not detected at either time point, these changes in chondrogenesis may reflect sensitivity of the pluripotential gap tissue to tension accumulation during lengthening. Future work with this in vivo model is focused on improving our understanding of the mechanisms behind this strain sensitivity.

Temporal and spatial characterization of regenerate bone in the lengthened rabbit tibia.

A rabbit model of bilateral tibial lengthening was used to investigate temporal and spatial changes in new bone volume and architecture during regenerate bone formation. Tibiae were lengthened 9.0 mm at 0.75 mm/day after a 6-day latency period. Animals were euthanized at four time points, and new bone volume and architecture within the distraction gap were assessed by microcomputed tomography and histomorphometry. New bone formation began before day 18 postsurgery and increased markedly between day 18 (completion of distraction) and day 24. This period of high bone formation activity might therefore be optimal for biologic and mechanical interventions aimed at enhancing bone regeneration. Regions of both endochondral and intramembranous bone formation were observed throughout the consolidation period. Significant increases in bone volume fraction were observed early in the consolidation period and were attributed to significant increases in trabecular thickness. This suggested that increased mineral density in the gap tissue with time was a consequence of increased osteoblast activity and associated trabecular thickening. New bone formation was shown to be highly oriented toward the distraction axis throughout lengthening. More bone formed consistently in lateral and proximal regions of the distraction gap, perhaps due to improved blood supply or progenitor cell availability in these areas. No differences in trabecular architecture were detected between regions having more or less bone volume, suggesting that bony tissue differentiation in all regions of the distraction gap was similar. Homotypical variations in measures of bone architecture were small; thus, these outcome variables seem appropriate for determining the effects of biological and mechanical interventions on bone regeneration in this animal model.

The use of ultrasound mean acoustic attenuation to quantify bone formation during distraction osteogenesis performed by the Ilizarov method. Preliminary results in five dogs.

RATIONALE AND OBJECTIVES: Management of distraction during Ilizarov limb lengthening remains primarily clinical and empirical. Estimates of tissue acoustic attenuation were evaluated for their ability to quantify bone formation within the distraction gap. METHODS: Five dogs had tibias lengthened by the method of Ilizarov. Mean acoustic attenuation measurements at multiple positions across the distraction gap were compared with corresponding x-ray computed tomography attenuation measurements. RESULTS: Computed tomography and ultrasound attenuation displayed similar quantitative behavior across the gap. Linear correlation between them ranged from R2 = .878 to R2 = .131. Fibrous interzone width estimates based on computed tomography and ultrasound attenuation measurements were correlated, based on our preliminary data with R2 = .519. These estimates are independent of the width of distraction. CONCLUSIONS: Ultrasound parallels computed tomography as a measure of bone formation within the distraction gap. Future studies are needed to improve acoustic attenuation data acquisition techniques and to evaluate their potential as a tool for optimizing early distraction rates in patients at risk for rate-related complications.

Marrow-derived progenitor cell injections enhance new bone formation during distraction.

Bilateral femoral distraction was performed in rats to investigate whether injections of marrow-derived mesenchymal progenitor cells could be used to facilitate new bone formation. The cells were isolated from whole marrow of 2-6-month-old Sprague-Dawley rats. One-year-old recipient Sprague-Dawley rats were divided into five experimental groups. Rats in groups I, II, and III received injections of mesenchymal progenitor cells on days 6 (beginning), 12 (middle), and 18 (end of distraction) after surgery, respectively. Those in group IV received injections of serum and carrier gel alone, and those in group V received no injections. Distraction zones were harvested at 36 days and analyzed for new bone volume within the distraction gap by three-dimensional microcomputed tomography. Significant increases in new bone volume were observed for femora injected with marrow-derived progenitor cells compared with contralateral femora and controls (no injection). The timing of the cell injections appeared to have no effect on the experimental outcome. Histologic analyses demonstrated active formation of new trabecular bone with marked osteoblastic activity and osteoid production. No qualitative differences in histologic appearances of new bone among rats in any of the five groups were seen. The results of in vitro lysis assays indicated that donor and recipient rats were not completely syngenic, leaving some doubt as to the reasons for observed increases in new bone formation. Future work will focus on attempting to repeat these experiments in a fully syngenic rat model. This rat distraction model can be used to explore the molecular and cellular behavior of these progenitor cells in a clinically relevant in vivo environment.

Intraoperative autologous transfusion in orthopaedic patients.

The cases of 175 consecutive patients who had intraoperative autologous transfusion during revision total hip arthroplasty, an elective operation on the spine, repair of trauma to the spine, or open reduction of a fracture of the acetabulum were reviewed to evaluate the applicability of this technique in orthopaedic operations. A separate group of forty-one consecutive patients who had open reduction of a fracture of the acetabulum or the spine before the introduction of the autotransfuser was reviewed and compared with the group that had autotransfusion. An autologous blood predeposit program was used for twenty-five of fifty-two patients who had a procedure on the hip and for fifty-one of fifty-five patients who had an elective procedure on the spine. The mean rate of red blood-cell salvage using the autotransfuser was 60 per cent over-all. The mean transfusion requirements were significantly less (p less than 0.001) in all groups of patients in whom the autotransfuser was used. Use of the autotransfuser reduced the mean requirement for banked blood in patients who had a fracture of the acetabulum from 3.8 to 2.3 units per patient, and significantly reduced the mean need for banked blood in individuals who had trauma to the spine from 2.7 to 1.8 units per patient (p less than 0.01). The use of prebanked autologous blood further reduced the mean requirement for homologous blood from 2.4 to 0.8 unit per patient in those who had revision total hip arthroplasty (p less than 0.005), and from 3.6 to 0.4 unit per patient in those who had an elective procedure on the spine (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Successive bilateral total knee replacement.

We studied the results of 304 posterior stabilized condylar knee arthroplasties, performed over a two and a half-year period, to compare unilateral, bilateral one-stage, and bilateral staged arthroplasty. The minimum length of clinical follow-up was two years. Using The Hospital for Special Surgery rating system, we found the clinical results to be identical for all three groups. The medical complications were similar in each group except that there was a higher incidence of thromboembolism and pulmonary embolism, as seen venographically, in the patients with staged procedures. We concluded that one-stage bilateral knee arthroplasty is preferable in a patient who requires replacement for severely arthritic knees.

Mortality after fracture of the hip in patients who have end-stage renal disease.

Thirteen fractures of the hip in twelve patients who had end-stage renal disease were treated over a ten-year period; these injuries included one intertrochanteric fracture, seven non-displaced fractures of the femoral neck, and five displaced fractures of the femoral neck. Twelve of the thirteen fractures were treated with an operation. Six patients (who had a total of six fractures) died within one year after the fracture. Two patients died as the result of sepsis related to the wound; the other four deaths were not directly related to the operation. Although the mortality rate in this group of patients was higher than that in a group of matched patients who had a fracture of the hip but who did not have end-stage renal disease, we were not able to demonstrate that this difference was significant, perhaps because of the small size of the sample. The mortality rate in these twelve patients was significantly higher, however, than that in matched patients who had end-stage renal disease but who did not have a fracture of the hip (p = 0.01).

Comminuted fractures of the posterior wall of the acetabulum. A biomechanical evaluation of fixation methods.

Reproducible simple fractures and osteotomies of the posterior wall of the acetabulum were created in twenty paired hemipelves from fresh human cadavera. Comminution was created with an additional fracture line that was either parallel (concentric comminution) or perpendicular (transverse comminution) to the posterior rim of the acetabulum. Under simulated weight-bearing, the stiffness of fixation of the transversely comminuted fractures that had been achieved with use of a reconstruction plate and screws was significantly higher than that achieved with fixation with screws alone (p < 0.05). The load to failure of the fixation of transversely comminuted fractures treated with a reconstruction plate and screws was also significantly higher than that of fixation of such fractures with screws alone (p = 0.05). The load to failure of the fixation of concentrically comminuted fractures was significantly higher when a reconstruction plate and accessory spring plates had been used than when a reconstruction plate alone had been employed (p < 0.05).

Results of treatment of displaced patellar fractures by partial patellectomy.

The results of partial patellectomy as a treatment for displaced patellar fractures were assessed retrospectively with use of clinical, radiographic, and isokinetic strength-testing criteria. Forty patients who had been followed for an average of 8.4 years were studied. In the extremity that had been operated on, the mean active range of motion was 94 per cent, the circumference of the thigh was 100 per cent, and the strength of the quadriceps was 85 per cent of these measurements in the contralateral extremity. The over-all result was rated as excellent in twenty patients, good in eleven, fair in six, and poor in three. There was a significant statistical correlation between the type of fracture and the outcome. The results of this study indicate that partial patellectomy can be an effective treatment for selected patellar fractures.

Deep-vein thrombosis after fracture of the pelvis: assessment with serial duplex-ultrasound screening.

Sixty patients who had had a major fracture of the pelvis and were in stable condition on the orthopaedic ward three to five days after the injury were tested serially with duplex ultrasound, beginning approximately seven days after the injury, in order to determine the incidence of deep-vein thrombosis. Contrast venography was performed to confirm all positive non-invasive studies. Deep-vein thrombosis developed in eight patients (approximately 15 per cent). The thrombosis was in the popliteal or a more proximal vein in six of the eight patients, whereas in two it was distal to the popliteal vein. In four patients, evidence of thrombosis developed after one or more normal duplex-ultrasound studies. In one patient, symptoms that were suggestive of deep-vein thrombosis developed fifty-two days after the injury (four days after the fourth normal duplex-ultrasound examination), and ascending venography was entirely normal. Another patient had a pulmonary embolus fifteen days after the injury, and on the same day a duplex-ultrasound study was positive for thrombosis. During six weeks of follow-up after discharge from the hospital, symptoms of deep-vein thrombosis or pulmonary embolism did not develop in any patient in whom serial duplex-ultrasound studies had been negative.

Success of exchange reamed intramedullary nailing for femoral shaft nonunion or delayed union.

OBJECTIVES: To investigate the success of exchange reamed femoral nailing in the treatment of femoral nonunion after intramedullary (IM) nailing, and to analyze factors that may contribute to failure of exchange reamed femoral nailing. DESIGN: Retrospective consecutive clinical series. SETTING: Level I trauma center and tertiary university hospital. PATIENTS: Twenty-three patients were identified whose radiographs failed to show progression of healing for four months after treatment with a reamed IM femoral nail. Nineteen patients had undergone primary IM nailing of an acute femoral shaft fracture, one patient had been converted to an IM nail after initially being treated in an external fixator, and three patients had previously undergone an unsuccessful exchange reamed nailing. INTERVENTION: All patients were treated by exchange reamed femoral nailing. The diameter of the new nail was one to three millimeters larger than that of the previous nail (the majority were two millimeters larger). The intramedullary canal was overreamed by one millimeter more than the diameter of the nail. Most of the nails were statically locked, and care was taken to avoid distraction of the nonunion site by reverse impaction after distal interlocking was performed or by applying compression with a femoral distractor. MAIN OUTCOME MEASUREMENTS: Radiographic evaluation of union was determined by the presence of healing on at least three of four cortices. Factors reviewed included the patient's age, smoking history, mechanism of injury, associated injuries, whether the initial fracture was open or closed, the pattern and location of the fracture, the type of nonunion, the increase in nail diameter, whether the nail was dynamically or statically locked, and the results of any intraoperative cultures. RESULTS: Tobacco use was found to have a detrimental impact on the success of exchange reamed nailing. All eight of the nonsmokers healed after exchange reamed nailing, whereas only ten of the fifteen smokers (66.7 percent) healed after exchange reamed nailing. Overall, exchange reamed femoral nailing was successful in eighteen cases (78.3 percent). Three patients achieved union with additional procedures. Intramedullary cultures were positive in five cases; all of these achieved successful union. CONCLUSIONS: Exchange reamed nailing remains the treatment of choice for most femoral diaphyseal nonunions. Exchange reamed IM nailing has low morbidity, may obviate the need for additional bone grafting, and allows full weight-bearing and active rehabilitation. Tobacco use appears to have an adverse effect on nonunion healing after exchange reamed femoral nailing.

Hip screw augmentation with an in situ-setting calcium phosphate cement: an in vitro biomechanical analysis.

OBJECTIVES/HYPOTHESIS: This study was performed to determine whether a new, in situ-setting calcium phosphate cement would have sufficient mechanical integrity to reinforce compression screw fixation of unstable intertrochanteric fractures. We compared the cut-out resistance of screws augmented with calcium phosphate cement to the cut-out resistance of screws augmented with polymethylmethacrylate (PMMA). We used PMMA as the standard for comparison because it is currently used clinically. Our hypothesis was that initial fixation strength with PMMA and calcium phosphate cement augmentation would not be significantly different from one another. STUDY DESIGN: Cut-out testing of compression hip screws in paired human cadaveric proximal femurs was performed before and after augmentation with PMMA or calcium phosphate cement. Bilateral testing was performed to allow pairwise comparisons of the materials used for augmentation, and repeated testing was done to provide an internal control for the effects of bone quality. The initial fixation of screws augmented with calcium phosphate cement was compared with that of screws augmented with PMMA. METHODS: Ten paired human femurs (mean age, 75 +/- 9.2 years) were implanted with Richards AMBI compression hip screws. Basicervical osteotomies were then performed, yielding isolated proximal fragments for mechanical testing. Preaugmentation cut-out tests were performed under displacement control, with cut-out continuing to five millimeters at two millimeters per second. The screws were then removed, and the screw tracks were filled with 2.0 cubic centimeters of PMMA (one side) or calcium phosphate cement (contralateral side). After augmentation, the screws were reinserted and the cements were allowed to harden for twenty-four hours. Postaugmentation testing followed the protocols for preaugmentation testing, and the initial fixation strength of screws augmented with calcium phosphate cement was compared with the initial fixation strength of screws augmented with PMMA using a two-way repeated measures analysis of variance. RESULTS: The cut-out behavior of screws augmented with calcium phosphate cement was not significantly different from the cut-out behavior of screws augmented with PMMA. With calcium phosphate cement, yield strength increased by 15.8 percent (from 1,354 +/- 632 newtons to 1,568 +/- 320 newtons); with PMMA, the yield strength increased by 26.8 percent (from 1,477 +/- 526 newtons to 1,834 +/- 225 newtons). However, only the increase with PMMA augmentation was significant at p < 0.05). The energy to yield increased significantly (41 percent, p < 0.05) with both types of augmentation (from 2,399 +/- 1,186 newton-millimeters to 3,378 +/- 857 newton-millimeters for calcium phosphate cement, and from 2,635 +/- 1,113 newton-millimeters to 3,741 +/- 426 newton-millimeters for PMMA), whereas the stiffness increased only slightly with PMMA augmentation (6.2 percent, from 481 +/- 180 newtons per millimeter to 511 +/- 92 newtons per millimeter) and fell slightly with calcium phosphate cement augmentation (10 percent, from 457 +/- 201 newtons per millimeter to 411 +/- 663 newtons per millimeter). CONCLUSIONS: The in situ-setting calcium phosphate cement investigated in this study compared favorably with PMMA in a single-cycle cut-out test of augmented compression hip screws in senile trabecular bone. Our results suggest that these materials may have promise as substitutes for PMMA in the salvage of compression hip screw fixation in elderly osteopenic patients with complex intertrochanteric fractures and that further study of their use in this application is warranted.

Physical therapy management of patients undergoing limb lengthening by distraction osteogenesis.

Limb lengthening by distraction osteogenesis and external fixation is used increasingly in the United States for a variety of orthopaedic conditions. Maintenance of joint motion, critical for successful outcomes, can be difficult to achieve. The rate of growth needed for distraction osteogenesis is faster than that of normal growing bone. Histogenesis of soft tissues must also occur to maintain the motion in joints above and below the limb being lengthened. Physical therapists in patients' home communities need to be knowledgeable about the aggressive management needed to prevent the loss of joint motion. This article introduces physical therapists to a commonly used external fixator, the procedure of distraction osteogenesis, and the role of functional loading. To assist in treatment planning, a physical therapy management plan is presented. Two case examples illustrate how therapists can assess a patient's status relative to the goals in the management plan and determine intervention priorities.

Clinical estimation of ilizarov fixator axial stiffness based on wire and half pin contributions.

A key parameter in the mechanical environment created in distraction osteogenesis is the axial stiffness of the external fixator. Mechanical testing of the frames with wire and half pins has been used to estimate the stiffness contributions of wires based on the span length and of half pins based on the offset length. A summation of the wire and half pin contributions appears to represent a suitable estimate for the axial stiffness of frames composed of a mixture of wires and half pins. Using this estimate, clinicians can make informed decisions regarding frame construction, and it may be possible to investigate the rate of bone formation relative to axial frame stiffness in the clinical setting.

Complex acetabular fractures.

Displaced acetabular fractures belonging to the associated fracture group described by Judet and Letournel present a formidable diagnostic and therapeutic challenge. Of 116 acetabular fractures, 31 had associated fracture types with follow-up evaluation of one year or longer. The patients' mean age was 30.7 years, their mean injury severity score was 15, and the average follow-up period was 21 months. Four patients had failed previous acetabular surgery. Operating time averaged 4.5 hours. Mean blood loss was 1150 cc. Clinical results were satisfactory in 77% of cases, with 11 excellent, 13 good, four fair, and three poor results. Complex acetabular fractures can be reduced by a combined anterior and posterior approach designed by the authors. This approach offers significant advantages for visualization and stabilization of these fractures. The combined approach is recommended for the surgeon who has mastered the single-approach techniques for standard, simple fracture patterns.